Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts formed of biocompatible materials (e.g., Dacron or expanded, porous polytetrafluoroethylene (PTFE) tubing) have been employed to replace or bypass damaged or occluded natural blood vessels. A graft material supported by framework is known as a stent graft. In general, the use of stent grafts for treatment or isolation of vascular aneurysms and vessel walls which have been thinned or thickened by disease (endoluminal repair or exclusion) are well known. Many stent grafts, are “self-expanding”, i.e., inserted into the vascular system in a compressed or contracted state, and permitted to expand upon removal of a restraint. Self-expanding stent grafts typically employ a wire or tube configured (e.g. bent or cut) to provide an outward radial force and employ a suitable elastic material such as stainless steel or Nitinol (nickel-titanium). Nitinol may additionally employ shape memory properties. The self-expanding stent graft is typically configured in a tubular shape of a slightly greater diameter than the diameter of the blood vessel in which the stent graft is intended to be used. In general, rather than performing an open surgical procedure which is traumatic and invasive to implant a bypass graft, stents and stent grafts are preferably deployed through a less invasive intraluminal delivery, i.e., cutting through the skin to access a lumen or vasculature or percutaneously via successive dilatation, at a convenient (and less traumatic) entry point, and routing the stent graft through the vascular lumen to the site where the prosthesis is to be deployed.
Intraluminal deployment is typically effected using a delivery catheter with a coaxial inner (plunger member) and an outer (sheath) tubes arranged for relative axial movement. The stent (or stent graft) is compressed and disposed within the distal end of an outer catheter tube in front of a stent stop fixed to the inner member. The catheter is then maneuvered, typically routed though a lumen (e.g., vessel), until the end of the catheter (and the stent graft) is positioned at the intended treatment site. The stent stop on the inner member is then held stationary while the sheath of the delivery catheter is withdrawn. The inner member prevents the stent graft from being withdrawn with the sheath. As the sheath is withdrawn, the stent graft is released from the confines of the sheath and radially expands so that at least a portion of it is in substantially conforming surface contact with a portion of the surrounding interior of the lumen e.g., blood vessel wall or anatomical conduit. As a convention used to describe the ends of devices implanted in the arterial system the proximal end of the stent graft is the end closest to the heart as taken along the path of blood flow from the heart, whereas the distal end is the end furthest away from the heart once deployed. An example of stent graft positioning and deployment is shown in FIG. 1, which is a FIGURE taken from U.S. Pat. No. 5,591,195 to Taheri et al.
FIG. 1 shows an aneurysm 30 in a vascular artery 32 (such as an aorta). A stent graft 34 spanning the aneurysmal sac 36 is show as just having been deployed from a delivery system 38. The stent graft 34 is constructed of a tubular graft (textile or cloth) material 40 which at each tubular end is radially expanded by zig zag type (Z-type) tubular stents 42, 44. A connecting bar 46 (shown in dashed lines) connects the two end stents 42, 44. The stent graft 34 deployed at the location of the aneurysm 30 creates a separate isolated flow path for blood through the lumen of the stent graft 34 such that the aneurysmal sac 36 of the aneurysm 30 is excluded and is no longer subject to the normal maximum blood pressure experienced in the vascular arterial system at the location of the aneurysm 30. Depending on the construction of the graft material 40 it may either seal immediately or provide a very slight permeable leakage (blush) which through the biological activity in the blood stream will cause the graft material 42 to be tightly sealed over time.
Stent grafts can also be used in patients diagnosed with aneurysms close to or crossing branch openings to renal arteries or other branch arteries (e.g., celiac, suprarenal, interior mesenteric). Stent graft designs with side openings are designed for use in regions of the aorta from which side branches feed blood to organs like the kidney, spleen, liver, and stomach. FIGS. 2 and 3 show examples from U.S. Pat. No. 6,030,414 to Taheri, as described therein. Such endovascular grafts have been designed for use where the proximal end of the graft is securely anchored in place, and fenestrations are configured and deployed to avoid blocking or restricting blood flow into the renal arteries. The endovascular graft must be designed, implanted, and maintain position in a manner which does not impair the flow of blood into the branch arteries.
Stent grafts 50, 60 with side openings or fenestrations 52, 54, 62, 64 are shown in FIGS. 2 and 3. Such fenestrations 52, 54, 62, 64 do not form discrete conduit(s) through which blood is channeled into each branch artery 51, 53, 61, 63, 67, 69. As a result, the edges of the graft surrounding the fenestrations 52, 54, 62, 64 could be prone to: i) the leakage of blood into the space between the outer surface 56, 66 of the aortic graft (stent graft 50,60) and the surrounding aortic wall 55, 65; or ii) post-implantation migration or movement of the stent graft 50, 60 causing misalignment of the fenestration(s) 52, 54, 62, 64 and the branch artery(ies) 51, 53, 61, 63, 67, 69—with resultant impairment of flow into the branch artery(ies).
FIG. 4 shows an alternate prior art configuration for a stent graft 70 having integrally constructed tubular branch members 71, 72, 73, 74, where the branch tubular members are placed into position using a series of guidewires 76, 77, 78, 79, where the top (proximal) end 80 fixed by a separately delivered stent (not shown) above the aneurysmal part of the aorta. A full explanation of the mechanism for delivery and final fixation of the stent graft with integral branches (as shown in FIG. 4) can be had by reference to U.S. Pat. No. 6,099,548 to Taheri the disclosure of which is incorporated herein by reference.
FIGS. 5 and 6 show an alternate arrangement for construction of a branch vessel connection. FIGS. 5 and 6 are examples taken from U.S. Pat. No. 6,059,824 to Taheri, incorporated herein by reference. In FIG. 5 the main stent body 90 once properly positioned in the main artery (not shown) has an opening wide annular land portion collar 93 aligned with side branching collateral arteries (not shown). The wide annular land portion collar 93 includes a series of inlets (or indentations) 94a, 94b. A collateral cylindrical stent body 92 is mated to the main stent body 90 through an annular land portion flange located at the proximal end of the collateral cylindrical body 92. The annular land portion collar 95 includes several detents 96a, 96b which are sized and spaced about the annular extent of the collateral collar 95 to position, hold and lock the collateral stent cylindrical body 92 mated to the main stent body 90. The detents, e.g. 96a, 96b, are received in the inlets e.g. 94a, 94b, of the main stent collar 93. An engagement balloon (not shown) located in the aorta is used to provide the force needed to lock the detents, e.g., 96a, 96b, and the inlets e.g., 94a, 94b, together.
FIGS. 7 and 8 show another prior art arrangement of a branch vessel connection to a stent graft. These FIGURES are similar to those in U.S. Pat. No. 5,984,955 to Wisselink, incorporated herein by reference. Referring now to FIGS. 7 and 8 together, a primary graft 100 includes a ring member 104 surrounding a side branch orifice 106 having a frustoconical member 102 extending from the graft 100. A side branch orifice 106 is aligned with the location of a branch artery (as seen in FIG. 8) and then a branch graft 110 is brought in through the main graft and snapped into position as the small ring member 114 and large ring member 116 at the ends of the tapered proximal portion 112 of the branch graft 110 are pushed into interfering engagement with the frustoconical member 102.
These examples of prior art devices to facilitate flow from an aneurysmal portion of the aorta into branch vessels show the complexity and space/volume requirements needed in the delivery system to deliver and accurately align such prior art systems. The use of fenestrations or openings in a tubular graft requires that a perimeter opening be sealed against the vascular wall to prevent the blood from passing through the tubular graft from continuing to pressurize and enlarge the surrounding aneurysmal sac. Such a main graft body can be provided with a flange or other fitting which is hard to compress to insert into a delivery catheter for deployment. And once the main stent graft body is in position then branch members need to be positioned with great care to provide a blood tight seal between the main graft body and the branch graft.
Thus, a need exists for a method and deployment system that simplifies alignment and reduces deployment forces needed to make a fluid tight connection between a main stent graft and a branch graft connected to a sidewall thereof. Ideally, such a branch graft is a part of a graft system that can treat aortic aneurysms at a location close to or at the location of a smaller vessel branching from the main vessel using a branch that makes a fluid tight connection to a port of the main graft.
Progress in this field looks to the development of new endovascular grafting systems and methods which a) may be useable for endovascular grafting in regions of a blood vessel (e.g., aorta) from which branch blood vessels (e.g., carotid, innominate, subclavian, intercostal, superior mesenteric, celiac, renal or iliac arteries) extend, and/or b) may enable more aortic aneurysm patients to be considered as candidates for endovascular repair, and/or c) may otherwise advance the state of the art of endovascular grafting to improve patient outcomes or lessen complications.